Taylor Swift, the pop music titan who has been notably apolitical in turbulent political times, broke her silence on Sunday and endorsed two Democratic candidates running for election in Tennessee.

In a post on Instagram, Ms. Swift said she planned to vote for Phil Bredesen, who is competing in a tight Senate race against a Republican candidate backed by President Trump, and Representative Jim Cooper, an incumbent who represents the Nashville area.

“I always have and always will cast my vote based on which candidate will protect and fight for the human rights I believe we all deserve in this country,” Ms. Swift wrote, adding that “I cannot vote for someone who will not be willing to fight for dignity for ALL Americans, no matter their skin color, gender or who they love.”

Ms. Swift’s political views had previously been left up to interpretation, and at times her silence was viewed as support for Mr. Trump as well as the alt-right movement. The singer is beloved by some white supremacists, who claim her as an Aryan goddess, and in 2017, her lawyers fought back against a blog post that portrayed her as a white supremacist figurehead.

While it is unclear whom she voted for in the last presidential election — she left fans to speculate based on a sweater she appeared to wear to the polls — Ms. Swift has finally made plain her political values, if not her voting record or party allegiance. She pledged support for L.G.B.T.Q. rights and racial and gender equality.

She wrote that she had previously been “reluctant” to publicly voice her political opinions. “Due to several events in my life and in the world in the past two years, I feel very differently about that now,” she wrote.

She then slammed Mr. Bredesen’s Republican opponent, Representative Marsha Blackburn, for her views on issues such as gay marriage and equal pay for women. “Her voting record in Congress appalls and terrifies me,” Ms. Swift said.

But like the public relations master she is, Ms. Swift left some room for speculation — and forgiveness. “For a lot of us, we may never find a candidate or party with whom we agree 100% on every issue, but we have to vote anyway,” she wrote.

Her post set off widespread discussion on social media, with the reaction largely falling along partisan lines. Conservatives dismissed her as a political know-nothing, and liberals celebrated, though some took issue with her endorsement of Mr. Bredesen, who had said he would have supported Justice Brett M. Kavanaugh’s contentious nomination to the Supreme Court.

But as with many things Ms. Swift does, it simply got people talking — and referring to Kanye West.

Mr. Bredesen, for his part, tweeted a screenshot of Ms. Swift’s post and thanked her for her “kind words.”